foo.c: In function 'main':
foo.c:9:11: warning: format '%s' expects argument of type 'char *', but argument 2 has type 'int' [-Wformat=]
  printf("%s",GNU(n));
          ~^  ~~~~~~
          %d
foo.c:7:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ^~~~~~~~~~~~~~
foo.c: In function 'GNU':
foo.c:16:2: warning: control reaches end of non-void function [-Wreturn-type]
  }
  ^

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